The present invention relates to a fume hood having an apparatus for measuring the quantity of air flow.
An object of a fume hood is to protect an experimenter from noxious fumes generated during experiment. Its important function is to exhaust noxious fumes generated within the fume hood.
In general, the exhaust capability of a fume hood is represented by the inlet velocity of ambient air flowing through an opening in the front face. That is to say, the quantity of air flow exhausted can be generalized as follows:
Quantity of air flow exhausted in one minute (m.sup.3 /minute)=Area of opening in the front face (m.sup.2).times.inlet air flow velocity (m/second).times.60.
The inlet air flow velocity depends upon the conditions of an experiment carried out in the fume hood including kinds and amounts of gases generated during the experiment.
For assuring the safety of a fume hood, therefore, it is necessary to confirm the operation condition of the fume hood, i.e., whether the inlet air velocity on the front face is suitable or not. Confirmation of this operation condition can be conducted by measuring a quantity of air flow discharged from the exhaust duct of the fume hood.
For the purpose of measuring the quantity of the discharged airflow, it is conceivable to install an air flow velocity sensor such as a hot-wire anemometer in the exhaust duct and to convert the flow rate of air discharged from the exhaust dust into an air velocity value for direct measurement.
In many cases, however, gases generated in the fume hood are extremely corrosive. Sometimes, mist is generated in addition to gases. Therefore, an air flow velocity sensor installed directly in the exhaust duct could not put up with a long-time use since the measuring part is attacked by a corrosive gas. In addition, mist sticked to the measuring part would cause mulfunction to obstruct precise measurement.